Rocket engine combustion chamber

ABSTRACT

An improved engine construction, such as a rocket engine construction is provided. The engine construction comprises a combustion chamber, a smooth wall nozzle, and a transition zone between the chamber and the smooth wall nozzle. The transition zone has a coolant system which includes a manifold formed from a non-copper material through which a coolant flows. In a high heat transfer embodiment, the transition zone includes an additional manifold formed from a copper based material.

BACKGROUND OF THE INVENTION

The present invention relates to a configuration of and a method ofassembling a regenerative cooled tubular rocket engine combustionchamber and nozzle.

A rocket engine combustion chamber contains the combustion ofpressurized fuel and oxidizer and the smooth acceleration of thecombustion products to produce thrust. Referring now to FIG. 1, theoxidizer and fuel are introduced under pressure through an injector 10attached to the top of the chamber 12. The combustion products underpressure advance to a de Laval nozzle 14 where the internal profileconverges to a throat 16. Here, the expansion of the combustion productsachieves sonic velocity. The convergent throat section is immediatelyfollowed by a divergent section 18. The combustion products are thenfurther accelerated to many times the speed of sound depending on theprofile of the divergent section, the oxidizer and fuel combination, thepressure of the combustion products and the external pressure. Theacceleration of gases creates thrust for the rocket engine.

Regenerative cooled combustion chambers take part of the flow ofcryogenic liquid propellant, usually fuel, to cool the walls of thecombustion chamber. The coolant flows along the outside of the chamberthrough passages or tubes. The coolant recycles the waste heat toincrease energy in the coolant. This increased energy in the coolantimproves the efficiency of the cycle. Regenerative cooled combustionchambers for rocket engines typically fall into three categories: milledchannel; platelet; and tubular construction.

In a milled channel construction, grooves of varying cross section arecut into the exterior of a liner, which assumes the shape of a de Lavalnozzle. A jacket is then built up over the open channels or acylindrical piece is slid on and vacuum compression brazed to the liner.

A platelet construction is similar to a milled channel but divides thelength of the liner into many smaller sections, which are then bondedtogether. A multiple piece jacket is then welded together over the linerand vacuum compression brazed together.

A tubular construction combustion chamber can be manufactured in twoways depending on its size. If the chamber is large enough in diameterto allow access, the tubes and braze material can be laid directly intoa single piece jacket and furnace brazed.

Assembly of smaller chambers starts by stacking forward tubes on amandrel in the shape of a de Laval nozzle. The tubes can be laidstraight along the length of the mandrel or can be spiral wrapped aroundthe mandrel. The tube ends are inserted into an inlet and exit manifold.Braze wire, paste and foil is inserted into all the cavities between thetubes. The tubes contain the pressurized propellants for cooling thechamber walls and picking up waste heat to use in the cycle. A multiplepiece jacket is then added to the outside of the tubes. The jacketsegments are then welded together or overlapping strips are addedbetween the jacket segments. The jackets and tubes are then furnacebrazed together.

The tubular construction chamber yields the lightest and most efficientchamber due to the larger heat transfer area and lower stressed tubecross sections. The tubular construction chamber integrity depends onthe quality of construction of the multiple piece jacket and brazecoverage for all joints between the tubes, jacket segments, andmanifolds.

The majority of the heat transfer between the combustion products andthe coolant in the combustion chamber occurs from the injector face downpast the throat to a few inches beyond the throat. It is here that theadvantages of the tubular construction chamber are best used to increasethe efficiency of the system. The point downstream of the throat whereheat transfer between the coolant and chamber drops off, is the bestplace to split the assembly into a combustion chamber (upstream) and anozzle (downstream) for manufacturing and assembly purposes. The nozzlecan be of any smooth wall construction to reduce costs.

Smooth wall nozzles can be any of four types: milled channel; platelet;ablative; and radiation. The first two have been described above. Theablative nozzle employs a coating on the chamber internal profile thatreleases a cooling gas as it is heated by the combustion products. Aradiation nozzle is made from a material that can take the heat inputfrom the combustion products and give positive structural margin whileonly relying on radiation cooling.

Current engines use a regenerative cooled milled channel chamber andnozzle, a regenerative cooled milled channel chamber with a regenerativecooled tubular nozzle, or a combination all tubular construction chamberand nozzle.

The difficulty with incorporating a regeneratively cooled tubularchamber with a smooth wall nozzle lies in the transition zone between atubular chamber wall profile and a smooth wall profile. Due to the verythin boundary layer of cooler gas flowing along the chamber profile, anysudden disturbance in the profile can lead to excessive temperatureslocally in the wall and the generation of shocks. Higher temperaturesreduce the material capability to withstand the internal coolantpressure loading and could lead to sudden failure. Shocks can lead tolocal pressure loading which can overload chamber wall material.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anassembly which allows a regenerative cooled tubular construction rocketengine chamber to be used with any smooth wall nozzle.

The foregoing object is attained by the assembly of the presentinvention.

In accordance with the present invention an improved engine, such as arocket engine, is provided. The engine comprises a combustion chamber, asmooth wall nozzle, and a transition zone between the chamber and thesmooth wall nozzle. The transition zone has a coolant system whichincludes a manifold formed from a non-copper material through which acoolant flows. In a high heat transfer embodiment, the transition zoneincludes an additional manifold formed from a copper based material.

A method of assembling a rocket engine combustion chamber having acombustion chamber, a smooth wall nozzle, and a coolant system with atransition zone between the combustion chamber and the nozzle isprovided. The method comprises the steps of forming a transition zone bypositioning at least one manifold having a plurality of holes on amandrel, inserting braze preforms into the holes, inserting a pluralityof tube assemblies into the holes, and furnace brazing the tubeassemblies to the at least one manifold.

Other details of the rocket engine combustion chamber of the presentinvention, as well as other objects and advantages attendant thereto,are set forth in the following detailed description and the accompanyingdrawings, wherein like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross section of a typical tubular constructionregenerative chamber;

FIG. 2 is a cross section of a transition zone from a tubular profile toa smooth wall nozzle;

FIG. 3 is a view of a section of a joint;

FIG. 4 is a view showing the leading edge of a leading edge manifold;

FIG. 5 is a view showing the radiused leading edge of the manifold ofFIG. 4;

FIG. 6 is a bottom view looking at the flowpath side of the manifold ofFIG. 4;

FIG. 7 is a cross section of the transition zone from tubular profile toa smooth wall profile; and

FIG. 8 is a cross section through a regeneratively cooled tubular rocketengine combustion chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The transition between a tubular flow path and a smooth wall flow pathmust be completed smoothly otherwise the heat input to the manifoldswill reduce the material properties below minimum acceptable values forthe stresses encountered. Part of this is to reduce any flow trips whichcould instigate heightened heat input to the manifolds.

Two configurations are described herein to achieve the ability totransition from a regenerative cooled tubular construction chamberprofile to a smooth wall nozzle profile. The first configuration is atwo piece manifold to counter very high heat transfer rates. The secondconfiguration is a one piece manifold to counter lower heat transferrates that permit a steel or nickel manifold.

The first configuration consists of tube assemblies with internalferrules brazed to the tubes and paired manifolds. A leading edgemanifold is made from a copper containing material, such as a copperbased alloy containing greater than 50% by weight copper, and an aftmanifold is made from a non-copper material, preferably steel or anickel containing material, such as a nickel based alloy containinggreater than 50% by weight nickel.

Referring now to FIG. 2, each tube assembly 30 has an internal ferrule32, which is configured with a round cross section. The free end 34 ofeach ferrule 32 has a tiered diameter with the diameter d near the freeend 34 being smaller than the diameter D near the tube 36. The largediameter D is sized for the braze gap 38 in the leading edge manifold 40which is formed from the copper containing material. The smallerdiameter d is sized for the braze gap 42 in the aft manifold 44. The useof the tiered internal ferrules 32 makes assembly of the ferrules endeasier with less chance of damage.

Referring now to FIGS. 3 through 6, to counter the expected high heatinput at the start of the transition zone, the leading edge manifold 40is formed from the copper containing material. Copper has highconductivity to take the increased heat input on the leading edge of thetransition zone. Holes 46 are drilled in the manifold to accept theferrules 32. The smooth wall 48 on the manifold 40 is in line with theround cross section of each tube 30. This creates a waterfall effect forthe expanding hot gas under the worst case tolerances. When the productsof combustion advance down the chamber 12 and past the throat 16, theinside of the chamber has a constantly expanding diameter. When the flowcomes to the interface between the tubes 30 and the manifold 32, theleading edge of the manifold flowpath must be sized so that its range ofdimensional tolerances is always at a larger diameter than that of thetube crown surfaces upstream. This allows the combustion products toadvance with the minimum of resistance and loss of energy. This is thewaterfall effect. The opposite of the waterfall effect would be the dameffect. This would be when the manifold leading edge is at a smalldiameter than that of the tube crown surfaces upstream. The smallerdiameter acts to block or interrupt the smooth flow of combustionproducts which results in localized heating and energy losses and thegeneration of shocks downstream.

On the upstream side of the interface there is the profile of the tubecrowns and on the downstream side, there is the flowpath profile of themanifold 40. The two profiles are line on line under the best casetolerances. On the flow path side 50 of the manifold 40, grooves 52 arecut between the holes at an angle to the flow path to transition fromthe gullies between the tubes up to the flat wall profile 54. Theleading edge 56 of the manifold 40 is radiused to smoothly transitioninto the grooves 52 in the manifold. The length of the grooves 52depends on the chamber application. The arrangement described hereinprovides a smooth contour without any flow trips.

Behind the leading edge manifold 40 is a manifold 44 of non-coppermaterial. As discussed above, preferred materials for the manifold 44are steel or a nickel based alloy. The non-copper material used for themanifold 44 preferably has a higher strength than the material used forthe manifold 40 to handle the coolant pressures at high flow pathtemperatures and the ability to be welded to the smooth wall nozzle 60and structural jacket 62. There is also a splice plate 61 between thejacket 62 and the smooth wall nozzle 60 on the outside of the coolantpassages. The splice plate is welded in place.

As can be seen in FIGS. 2 and 3, the manifold 44 has a series of holes162 to receive the free ends 34 of the ferrules 32. The holes 162 aresmaller in diameter than the holes 46. The holes 162 have a length whichis sufficient enough to accommodate any variation in ferrule end length.

The primary braze for the ferrules 32 to contain the blow off load ofthe coolant pressure is in the manifold 44. The aft manifold 44 and theferrules 32 are also brazed to the leading edge manifold 40 to improveconductivity from the material forming the manifold 40 to the othermaterials and to prevent any leakage from the flow paths into the joint.

The second configuration shown in FIG. 7 is for lower level heattransfer that permits use of a single manifold 70 formed from anon-copper material. In a preferred embodiment, the manifold 70 isformed from a single piece of steel or a nickel based alloy containingmore than 50% nickel. The internal passages or holes and the grooves cutinto the flow path of the manifold 70 are the same as for the firstconfiguration. The method of installing the tube assemblies 30 with theinternal ferrules 32 into the manifold 70 is the same as for the firstconfiguration.

The method of assembly is the same for both of the above configurations.First, the manifold or manifolds are positioned on a mandrel. Brazepreforms are then inserted into the holes in the manifold(s). The brazepreforms may be formed from any suitable braze material known in theart. The braze preforms 71 are tubular in nature and have bores whichallow the tube assemblies and the internal ferrules to be inserted intothe manifold(s). The braze preforms 71 are helical coils of braze wiremade to fit in the diameter of the manifold holes. The manifold holesare stepped to trap the braze preform 71 in place under the ferrules 32.Next, one by one insert the tube assemblies 30 into the manifold(s)until all of the tube assemblies have been inserted. Adjust the tubesprofiles and gaps between tubes according to braze requirements. Furnacebraze the manifold assembly after the opposite end of the tubes havebeen prepared for brazing. The jacket 62 can be included in the brazingprocess or added later after all repair brazing is completed. Inspectall braze joints for coverage and braze repair as required using anysuitable means known in the art. Weld on the smooth wall nozzle 60 toseal the coolant passages. The nozzle 60 and the splice plate 61 closethe coolant passages in the chamber so that the coolant passages in thenozzle flow through to the chamber without any leakage. By sealing thecoolant passages, it is meant that coolant passages are confined withinthe bounds of the chamber, nozzle and splice plate by leak free weldedstructural joints.

The chamber is joined to the leading edge of the manifolds in severalways. The ferrules on the tube assemblies are brazed to the holes in themanifold. A coating 75 of material similar to the tube material isapplied over the tubes 30 which also bonds to the outer surface of themanifold. The jacket 62 is then installed over the coating 75 and weldedto the outer surfaces of the manifold. A later furnace braze operationjoins the jacket 62 to the coating 75.

In accordance with the present invention, referring to FIG. 8, a rocketengine configuration using a regenerative cooled tubular constructionrocket engine chamber 80 and a smooth wall nozzle is provide whilesatisfying assembly and system requirements of an engine cycle withoutproducing flow path shocks or overheating of the chamber walls at thejoint.

It is apparent that there has been provided in accordance with thepresent invention a rocket engine combustion chamber which fullysatisfies the objects, means, and advantages set forth hereinbefore.While the present invention has been described in the context ofspecific embodiments thereof, other alternatives, modifications, andvariations will become apparent to those skilled in the art having readthe foregoing description. Accordingly, it is intended to embrace thosealternatives, modifications, and variations which fall within the broadscope of the appended claims.

1. An engine comprising: a combustion chamber; a smooth wall nozzle; atransition zone between said chamber and said smooth wall nozzle, saidtransition zone having a coolant system which includes a manifold formedfrom a non-copper material through which a coolant flows; an additionalmanifold formed from a copper based material; said transition zoneincluding a plurality of tube assemblies for conveying said coolant andsaid additional manifold having a plurality of holes for receiving saidplurality of tube assemblies; each tube assembly having a round crosssection and said additional manifold having a smooth wall in line withthe round cross section of each said tube assembly; and said additionalmanifold having a flow path side and a plurality of grooves in betweensaid holes to transition from gullies between the tubes up to a flatwall profile.
 2. An engine comprising: a combustion chamber; a smoothwall nozzle; a transition zone between said combustion chamber and saidsmooth wall nozzle; said transition zone having a coolant system whichincludes a first manifold abutting said nozzle and being formed from anon-copper material through which a coolant flows and a second manifoldabutting said first manifold; said second manifold being formed from amaterial different from said non-copper material; said first manifoldhaving a plurality of holes and said second manifold having a pluralityof holes which align with said holes in said first manifold; and saidcooling system including a plurality of internal ferrules having a freeend and each said internal ferrule passing through one of said holes insaid second manifold and having its free end disposed in one of saidholes in said first manifold.
 3. An engine according to claim 2, whereineach of said internal ferrules has a first portion with a first diameterand said free end has a second diameter smaller than said firstdiameter.
 4. An engine according to claim 3, wherein said first portionresides in one of said holes in said second manifold.
 5. An engineaccording to claim 2, wherein each said internal ferrule is brazed tosaid first manifold.
 6. An engine comprising: a combustion chamber; asmooth wall nozzle; a transition zone between said combustion chamberand said smooth wall nozzle; said transition zone having a coolantsystem which includes a first manifold abutting said nozzle and beingformed from a non-copper material through which a coolant flows and asecond manifold abutting said first manifold; said second manifold beingformed from a material different from said non-copper material; andwherein said second manifold comprises means for creating a waterfalleffect for expanding hot gases and for allowing combustion products toadvance with a minimum of resistance and loss of energy.